Indium-tin oxide thin films by metal-organic decomposition

In2O3-SnO2 films were produced by thermal decomposition of a deposit which was dip coated on borosilicate glass substrates from an acetylacetone solution of indium and tin acetoacetonate. Thermal analysis showed complete pyrolysis of the organics by 400 °C. The thermal decomposition reaction generated acetylacetone gas and was found to be first order with an activation energy of 13.6 Kcal/mole. Differences in thermal decomposition between the film and bulk materials were noted. As measured by differential scanning calorimetry using a 40 °C/min temperature ramp, the glass transition temperature of the deposited oxide film was found to be ∼462 °C, and the film crystallization temperature was found to be ∼518 °C. For film fabrication, thermal decomposition of the films was performed at 500 °C in air for 1 h followed by reduction for various times at 500 °C in a reducing atmosphere. Crystalline films resulted for these conditions. A resistivity of ∼1.01 × 10−3 Ω · cm, at 8 wt. % tin oxide with a transparency of ∼95% at 400 nm, has been achieved for a 273 nm thick fil

Wear and frictional mechanisms of copper-based bearing alloys

The present study investigated the role of alloy microstructure and surface roughness on wear and friction behavior of leaded and unleaded tin bronzes. Ball-on-disk experiments were carried out under dry conditions with steel balls sliding against bronze disks. Scanning electron microscopy (SEM), energy dispersive electron microscopy (EDX), x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy were performed to analyze the sliding tracks and the ball scars. The wear reducing effect of lead was associated to the formation of an oxidized lead rich layer. When no such film formed on the leaded bronze wear was more severe than in case of unleaded bronze. Nevertheless, the presence of lead in the alloy was a necessary but not sufficient condition to obtain a smeared layer and thus a lubricating effect of the leaded alloy. Two mechanistic hypotheses were formulated to explain the formation of the smeared layer. (C) 2011 Elsevier B.V. All rights reserved

Homogenization and free-vibration analysis of elastic metamaterial plates by Carrera Unified Formulation finite elements

This work focuses on the assessment of a novel so-called “homogenization method” allowing to transform a heterogeneous material with inclusions or holes into an equivalent homogeneous material with equal mechanical behavior. The aim is to avoid meshing holes of the real material in finite-element codes, thus improving computation time for further analysis of the material. Typical periodic structure of passive acoustic metamaterial plates is considered here, with inclusions/holes that should improve the acoustic performances in the low-frequency range. The three-dimensional homogenization method, based on Carrera unified formulation (CUF) [E. Carrera, M. Cinefra, M. Petrolo, and E. Zappino. Finite Element Analysis of Structures through Unified Formulation. John Wiley & Sons, 2014] and Mechanics of Structure Genome, is assessed for a perforated plate made of a linear elastic material with periodic arrangement of holes. Different configurations of the metamaterial plate are considered, changing the number of the holes. The results obtained from the free-vibration analysis of the homogenized plates, performed by higher-order two-dimensional models contained in CUF, are compared with ABAQUS results and both numerical and experimental results provided in literature

A note on alpha-vacua and interacting field theory in de Sitter space

We set up a consistent renormalizable perturbation theory of a scalar field in a nontrivial alpha vacuum in de Sitter space. Although one representation of the effective action involves non-local interactions between anti-podal points, we show the theory leads to causal physics, and we prove a spectral theorem for the interacting two-point function. We construct the renormalized stress energy tensor and show this develops no imaginary part at leading order in the interactions, consistent with stability.Comment: 22 pages, 2 figures, latex. v4 some clarifications, some typos fixe

Non-pharmaceutical interventions and risk of COVID-19 infection: survey of U.K. public from November 2020 – May 2021

Introduction: Non-pharmaceutical interventions (NPIs), such as handwashing, social distancing and face mask wearing, have been widely promoted to reduce the spread of COVID-19. This study aimed to explore the relationship between self-reported use of NPIs and COVID-19 infection. Methods: We conducted an online questionnaire study recruiting members of the UK public from November 2020 to May 2021. The association between self-reported COVID-19 illness and reported use of NPIs was explored using logistic regression and controlling for participant characteristics, month of questionnaire completion, and vaccine status. Participants: who had been exposed to COVID-19 in their household in the previous 2 weeks were excluded. Results: Twenty-seven thousand seven hundred fifty-eight participants were included and 2,814 (10.1%) reported having a COVID-19 infection. The odds of COVID-19 infection were reduced with use of a face covering in unadjusted (OR 0.17 (95% CI: 0.15 to 0.20) and adjusted (aOR 0.19, 95% CI 0.16 to 0.23) analyses. Social distancing (OR 0.27, 95% CI: 0.22 to 0.31; aOR 0.35, 95% CI 0.28 to 0.43) and handwashing when arriving home (OR 0.57, 95% CI 0.46 to 0.73; aOR 0.63, 95% CI: 0.48 to 0.83) also reduced the odds of COVID-19. Being in crowded places of 10–100 people (OR 1.89, 95% CI: 1.70 to 2.11; aOR 1.62, 95% CI: 1.42 to 1.85) and > 100 people (OR 2.33, 95% CI: 2.11 to 2.58; aOR 1.73, 95% CI: 1.53 to 1.97) were both associated with increased odds of COVID-19 infection. Handwashing before eating, avoiding touching the face, and cleaning things with virus on were all associated with increased odds of COVID-19 infections. Conclusions: This large observational study found evidence for strong protective effects for individuals from use of face coverings, social distancing (including avoiding crowded places) and handwashing on arriving home on developing COVID-19 infection. We also found evidence for an increased risk associated with other behaviours, possibly from recall bias

Quantum field theory and Hopf algebra cohomology

We exhibit a Hopf superalgebra structure of the algebra of field operators of quantum field theory (QFT) with the normal product. Based on this we construct the operator product and the time-ordered product as a twist deformation in the sense of Drinfeld. Our approach yields formulas for (perturbative) products and expectation values that allow for a significant enhancement in computational efficiency as compared to traditional methods. Employing Hopf algebra cohomology sheds new light on the structure of QFT and allows the extension to interacting (not necessarily perturbative) QFT. We give a reconstruction theorem for time-ordered products in the spirit of Streater and Wightman and recover the distinction between free and interacting theory from a property of the underlying cocycle. We also demonstrate how non-trivial vacua are described in our approach solving a problem in quantum chemistry.Comment: 39 pages, no figures, LaTeX + AMS macros; title changed, minor corrections, references update